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A Cox regression analysis showed a significant association between a gout diagnosis and subsequent breast cancer diagnosis in the total population.
Results of a retrospective cohort study demonstrated an association between gout and a subsequent breast cancer diagnosis, especially in younger patients, according to researched published in Springer.1
Breast cancer is the most common cancer in women worldwide with 2.1 million newly diagnosed cases in 2018. Approximately 20% of breast cancer-related deaths and poor outcomes regarding recurrence and reduced survival are attributed to modifiable risk factors including obesity, alcohol use, and reduced physical activity.2
“The association between breast cancer and gout as a common inflammatory disease has attracted much interest during the past few years,” wrote Niklas Gremke, MD, Department of Gynecology and Obstetrics, University Hospital Marburg, Philipps-University Marburg, Germany, and colleagues. “Despite being one of just a few curable rheumatic diseases, both the prevalence and incidence of gout are increasing across the globe so that it is being hypothesized in the literature that a modern gout epidemic is currently developing that is on a similar scale to the obesity epidemic. This increasing disease burden of gout is a consequence of lifestyle changes, obesity and dietary factors.”
The cumulative incidence of breast cancer following a gout diagnosis and association between the 2 diagnoses were analyzed in 67,598 adult, female, primary care patients in 1284 general practices Germany between January 2005 and December 2020. Data was extracted from the Disease Analyzer database (IQVIA), which covers 3% of all German private practices. Inclusion criteria included a 12-month observation period prior to the index date and a 6-month follow-up time afterwards.
Patients with gout (n = 33,799) were matched to non-gout patients (n = 33,799) using propensity score matching (1:1) based on average yearly consultation frequency during the follow-up period, diuretic therapy, diabetes, obesity, and chronic bronchitis/chronic obstructive pulmonary disease (COPD) diagnoses. Kaplan-Meier curves were used to determine the 10-year cumulative incidence of breast cancer among the cohorts, which were then compared using a log-rank test. A univariable Cox regression analysis evaluated the association between breast cancer and gout.
The mean age of patients was 66 years, patients visited their physicians an average of 6.9 times per year during the follow-up period, and many (45.2%) received diuretics within 12 months prior to the index date.
At the 10-year mark, 4.5% of patients with gout and 3.7% of non-gout patients were diagnosed with breast cancer; an incidence of 4.5 vs 3.9 cases per 1000 patient-years, respectively. The Cox regression analysis showed a significant association between a gout diagnosis and subsequent breast cancer diagnosis in the total population (hazard ratio [HR]: 1.17; 95% confidence interval [CI]: 1.05 – 1.31). Based on the age-stratified analyses, gout was only strongly associated with breast cancer in patients aged ≤ 50 years 50 (HR: 1.58; 95% CI: 1.10–2.27); however, it was not significant in women aged over 50 years.
Investigators noted several strengths, including the large European outpatient database containing data from roughly 7.8 million patients in Germany with validated diagnoses. Additionally, it contains data generated directly from practice computers based on patent data and has been used in several studies in various disciplines. Propensity score matching based on obesity and diabetes also strengthened the study as they are historically related to breast cancer.
However, the database does not contain information on other confounding factors, such as socioeconomic status and alcohol, which are other important risk factors for developing gout. Further, there is a lack of hospital information and data on mortality.